LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
M.Sc. DEGREE EXAMINATION – STATISTICS
|
FOURTH SEMESTER – APRIL 2006
ST 4803 – STATISTICAL PROCESS CONTROL
Date & Time : 22-04-2006/9.00-12.00 Dept. No. Max. : 100 Marks
SECTION A
Answer all the questions 10 x 2 = 20
- Discuss the statistical basis underlying the general use of 3 – sigma limits on control charts.
- Define rational subgroup concept.
- How is lack of control of a process determined by using control chart techniques?
- What is process capability ratio (PCR)?
- Why is the np chart not appropriate with variable sample size?
- Explain an attribute single sampling plan.
- What purpose does an OC curve serve?
- Define AOQ.
- Define a). Specification limit. b). Natural tolerance limit.
- Explain the concept of TQM.
SECTION B
Answer any five questions 5 x 8= 40
- What are the dimensions of quality? Explain.
- A quality characteristic is monitored by a control chart designed so that the probability that a certain out of control condition will be detected on the first sample following the shift to that is 1 – b. Find the following:
a). The probability that the out of control condition will be detected on the second sample following the shift.
b). The expected number of subgroups analyzed before the shift is detected.
- A control chart for the fraction non-conforming is to be established using a CL of p = 0.10. What sample size is required if we wish to detect a shift in the process fraction non-conforming to 0.20 with probability 0.50?
- Explain the method of constructing control limits for X – bar and R charts when the sample sizes are different for various subgroups.
- In designing a fraction non-conforming chart with CL at p =0.20 and 3-sigma control limits, what is the simple size required to yield a positive LCL? What is the value of n necessary to give a probability of .50 of detecting a shift in the process to 0.26?
- Estimate process capability using X – bar and R charts for the power supply voltage data . If specifications are at 350 + 5 V, calculate PCR, PCRk and PCRkm. Interpret these capability ratios.
Sample # | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
X1 | 6 | 10 | 7 | 8 | 9 | 12 | 16 | 7 | 9 | 15 |
X2 | 9 | 4 | 8 | 9 | 10 | 11 | 10 | 5 | 7 | 16 |
X3 | 10 | 6 | 10 | 6 | 7 | 10 | 8 | 10 | 8 | 10 |
X4 | 15 | 11 | 5 | 13 | 13 | 10 | 9 | 4 | 12 | 13 |
- Find a single sampling plan for which p1 = 0.05, a = 0.05 p2 = 0.15 and b = 0.10.
- What are chain sampling and skip-lot sampling plans?
SECTION C
Answer any two questions 2 X 20 = 40
- a) Distinguish between c and u charts. Explain the situations where c and u charts are applicable and are the limits obtained for these charts.
- b) Find 0.900 and 0.100 probability limits for a c-chart when the process average is equal to 16 non- conformities. (14+6)
- a) Write a detailed note on the moving average control chart.
- b) What are modified control charts?. Explain the method of obtaining control limits for modified control charts. (8+12)
- a) Outline the procedure of constructing V-mask.
- b) What is Exponentially Weighted Moving Average control chart?. (15+5)
- a) Write a detailed note on six-sigma quality.
- b) Explain with an illustration the method of obtaining the probability of acceptance for a triple sampling plan. (10 + 10)
Latest Govt Job & Exam Updates: